There are several means that have been employed to accomplish mechanical work by machines. Most of these can be classified into electromagnetic, electromechanical, hydraulic, or pneumatic means.
The electromagnetic devices utilize electrically generated magnetic fields interacting with highly permeable material moving elements to accomplish work. They have been successful in applications involving rapid mechanical response but tend to be non-linear in force application and present design complications for large displacement applications. They require large amounts of power from some external source, usually a sophisticated power conditioner/driver controller and they are noisy.
The electromechanical devices utilize an electric motor and frequently a gear train combination. Their most natural application is in those cases where rotary motions are suitable. This rotary motion character frequently drives the design considerations. In many cases at the output, rotary-to-linear mechanical conversion is necessary to satisfy the needed motion. Due to the numerous moving parts it is difficult to build an economical, and at the same time reliable and efficient, system using this class of device for most applications. They also tend to make excessive noise.
Hydraulic systems have found application where high force in combination with long linear motion is desired. These actuators require a complicated assortment of ancillary hardware such as electric or combustion engine motive means, fluid pumps, hoses/pipes, valves, and linear or rotary motion actuators. Due to very high internal operating pressures the components tend to be heavy. It is difficult to design these systems to operate efficiently. The closed circulation hydraulic working fluid tends to leak with attendant concern about failure, contamination and safety.
Current pneumatic systems have many of the features associated with their hydraulic cousins except that the working medium is a gas rather than a liquid. Prior art for supplying gas to pneumatic mechanical actuators is very similar to hydraulic systems in that they have also involved complicated arrangements of motors, pumps, valves and hoses to provide the working gas to the work output device. They too present hazards in operation.
It would be too exhaustive to review the vast scope of prior art in all the classes mentioned above. The new art in the present device is the use of metal hydride material in association with thermoelectric components to provide the motive means in close proximity to the pneumatic driven devices thereby eliminating the ancillary components. Nothing can be found in existing patents that show thermoelectric components being used with metal hydrides. The physical and thermal properties of hydrides are the most important component in the present invention, so research of prior art will focus on hydride materials and their application. There are several inventions that utilize metal hydride materials in association with heat. Five of these will be discussed to give the reader insight into prior art involving metal hydride materials. The first will be a fire extinguisher nozzle actuation concept. The second will be the application of metal hydrides to a solar powered water pump. The third will be hydrogen compressors. Two involve converting low grade heat to high grade heat to perform work external to the system.
In U.S. Pat. No. 4,377,209 to P. M. Golben, dated Mar 22, 1983, a hazardous building fire activates an alarm element that contains hydride material which releases hydrogen gas. This gas then motivates a piston connected to a piercing element that triggers another gas supply which dispenses fire suppressant. This application relies on heat energy, from a fire in the monitored space, to heat the metal hydride in the fire monitoring element to affect release of hydrogen and subsequent motivation of the piston to activate the fire extinguishing system. This design does not provide or require a high degree of control in that it relies on the fire to be extinguished and the element cooled down so the metal hydride can reabsorb the hydrogen and reset the trigger piston. This is a specific application to fire detection and suppression devices.
U.S. Pat. No. 4,282,931 to P.M. Golben dated Aug. 11, 1981 describes a metal hydride source which is activated by a resistance heater which is powered by an external source of electricity and is made of a specific material and design embodiment but it does not contain several important features of the present invention such as heat energy control which our invention provides with a thermoelectric module nor does it utilize opposed acting gas generating elements. The patent to Golben does not address the needs of overall efficiency when operating in conjunction with an external reciprocating working system.
U.S. Pat. No. 4,884,953 to P. M. Golben dated Dec. 5, 1989 describes a solar powered pump with electrical generator which utilizes the temperature difference between heat obtained from solar energy collection panels and pumped ground water to operate the pump unit. This patent teaches how to apply the unique properties of metal hydrides to efficiently operate a ground water pumping system. Another novel feature of this patent is use of the work being done by the metal hydride engine to additionally operate an electrical generator and storage unit which is used to operate the controls for the water flow so the system will work. This use of metal hydrides is in the construction of a low temperature heat engine and does not utilize thermoelectric elements.
U.S. Pat. No. 4,402,187 dated Sep. 6, 1983 to P. M. Golben and M. J. Rosso, Jr. describes a hydrogen gas compressor concept that utilizes the unique properties of metal hydrides to compress hydrogen without mechanical moving parts. It does not involve thermoelectrics in any way.
U.S. Pat. No. 3,504,494 dated Apr. 7, 1968 to W. E. Winche describes a method of using metal hydrides to intermittently provide heat pulses sufficient to generate steam which can then be used to perform work. The focus of this invention provides a technique to charge a metal hydride bed with energy which, when released during a shortened duty-cycle, can boil water and produce steam which can perform work in a dynamo, mechanical device, radiator, etc. where some of the energy is extracted from the steam. After performing this work the system is required to reject heat to ambient environment, condense the steam to water, and store the water while the low grade heat source recharges the initial metal hydride bed. This invention utilizes two metal hydride beds sharing the same volume of hydrogen gas to transform low grade heat to high grade heat in order to generate steam which is then used to perform work intermittently. The method of obtaining a higher temperature T.sub.1 in the first bed 2 than T.sub.2 in the second bed 4, both of which are above ambient temperature, is not disclosed in the text of the patent. This invention requires the use of numerous valves, tanks, heat exchangers etc. and would require a fairly sophisticated controller unit to operate the valving sequence. The system shown also relies on gravity to recharge the boiler feed tank for its proposed operation to generate steam as a primary working fluid. Our invention uses two separate gas volumes, whose temperature is controlled by a thermoelectric unit, and uses the hydrogen gas as the working fluid to actuate the mechanical work element directly.
U.S. Pat. No. 4,085,590 dated Apr. 25, 1978 to Powell et. al. incorporates and improves on Winche, by eliminating the water and steam generation for a secondary working fluid, and it also elaborates on specific design features of a metal hydride containment unit to be used for hydrogen compression (FIG. 2). The object of the invention is to produce high energy hydrogen gas working fluid power for directly driving turbine generator units from a low energy heat source but on a more continuous basis than Winche. The plurality of hydride beds and the complexity of the system that Powell proposes is much greater than Winche due to the large number of valves, pumps, heat exchangers, piping and fans needed for cycling the cross-fed hydride beds and imputing and rejecting heat energy from the system. As in Winche, the proposed system uses only one volume of hydrogen working gas. Our invention uses a thermoelectric unit to simultaneously input and extract heat from two separate hydrogen generators. This provides high efficiency operation. By reversing current in the thermoelectric unit rapid reversal of force can be achieved in the attached pneumatic mechanical device.